1. Field of the Invention
The present invention generally relates to a trigger mechanism and a firearm containing the same. More particularly, the present invention is directed towards a trigger mechanism and a firearm that is safe and has a lightweight and short trigger pull.
2. Description of the Prior Art
Various types of firearms can be categorized according to various different characteristics of the firearms. For example, firearms arms can be classified according to the different trigger designs.
Most military or competitive shooters appear to have adopted a trigger design called a two-stage trigger. A two-stage trigger is designed so that when the shooter “squeezes” the trigger (i.e. exert a force with his/her finger on a “trigger shoe”), there is an immediate and relatively large displacement of the trigger shoe (i.e. the first stage). This is followed by an abrupt and definitive stop and is referred to as a first stage. At this point, an additional force is gradually applied until (a sudden) discharge occurs (i.e. the second stage). Thus, a two-stage trigger is characterized by a light squeeze that takes up an initial slack, followed by an additional squeeze, which leads to a sudden release of the firing mechanism.
In contrast, most hunters or casual shooters appear to prefer a single stage trigger. A single stage trigger is designed so that upon squeezing the trigger, perceptible displacement of the trigger does not take place until the discharge of the firearm. Thus, the single stage trigger is characterized by a gradually applied squeeze followed by the sudden release of the firing mechanism.
Regardless of which trigger designs are employed, important functional goals of a high quality trigger mechanism design include, to name a few, safety, lightweight trigger pull, nearly imperceptible movement of the trigger shoe during discharge, and a “crisp” feel during discharge. For example, lightweight trigger pull is desired so that the position of the firearm will not be influenced during discharge of the firearm (i.e. for accuracy). Safety is a major concern so that accidental (unintentional) discharge of the firearm is prevented.
Obtaining a lightweight trigger while maintaining safety has been difficult. As such, trigger mechanism designs traditionally employed a trade-off strategy wherein heavy trigger pull was employed to prevent accidental discharge of the firearm.
Most trigger mechanisms incorporate a sear. A sear is typically characterized by two hardened steel components engaging (bearing upon) one another to maintain the trigger mechanism in a set configuration. Typically, the engagement of the two sear components is characterized by a slight overlap with each other to obstruct motion until a trigger is pulled. Upon pulling the trigger, these two components are designed to disengage in order to allow discharge of the firearm.
In the two-stage trigger design, a relatively large sear engagement of about 1.5 mm can be employed. (Sear engagement is the overlap of the two sear components, wherein in the present invention, the two sear components are a sear and a sear catch.) However, the relatively large displacement of the trigger in the first stage causes the sear to become almost completely disengaged, so that a nearly imperceptible movement of the trigger and a “crisp” feel can be obtained during the second stage.
In the single-stage trigger design, sear engagement is on the order of 0.25-0.38 mm, which is only about 3-5 times more than the diameter of human hair. Such small or slight sear engagement is provided so that a “crisp” feel can be provided during discharge. As such, these firearms rely heavily on their safety mechanisms and stiff springs to maintain sear engagement.
However, certain problems exist with such an approach. The surfaces and edges of the two hardened steel components of the sear can degrade over time by wear, corrosion, and additional factors. Therefore, accidental discharge of the firearm can suddenly occur without warning after prolonged use or storage, especially in a corrosive environment.
Even the presence of a safety mechanism may not be satisfactory. For example, if a safety mechanism functions so as to maintain sear engagement, sear degradation can result in an accidental discharge of the firearm regardless of whether the safety mechanism is in place or not. In addition, even if a safety mechanism of a firearm functions to obstruct the motion of the firing pin assembly independently of the sear mechanism, accidental discharge can nevertheless occur. For example, sear degradation may cause an accidental discharge to occur as soon as the safety mechanism is disengaged.
Therefore, a trigger exhibiting minimal movement, a lightweight trigger pull, and a large (and therefore safe) sear engagement before discharge would provide significant improvements.